Preheat oven to 220°C. Grease a 11cm x 33cm (base measurement) fluted tart tin with a removable base.
Cut pastry into 3 pieces to fit the tin. Line the tin with the pastry pieces and trim excess. Cover the pastry with baking paper and fill with pastry weights or rice. Bake for 15 mins. Remove paper and weights or rice.
Meanwhile, reserve 60g of the spinach. Heat the oil in a large frying pan over medium-high heat. Cook the onion and garlic, stirring, for 3-5 mins or until onion softens. Add remaining spinach and cook, stirring, for 2 mins or until just wilted. Transfer to a large bowl. Cool for 5 mins. Stir in the egg, ricotta, parmesan and half the fetta.
Reduce oven temperature to 180°C. Spoon the spinach mixture into pastry case. Sprinkle with remaining fetta. Bake for 25-30 mins or until filling is set and golden.
While the tart is cooking, place the tomatoes on a baking tray. Spray with olive oil spray. Roast with the tart for the last 15 mins of cooking or until tomatoes are soft.
Arrange the tomatoes on the tart and top with reserved spinach.